Why would your PPC need to be propped up? A quick test suggests to me that it would be comfortable to look down at a PPC lying on a flat surface (or your lap) and type holding a credit card.
If you need to to data input whilst holding your device at the same time though, this obviously won't be suitable.
I think it could be a useful gadget, and not just for data input - it could also be used as a music remote control for Mortplayer/WMP etc, or a page scroller when reading an e-book.
I'd consider buying it if it were £10 cheaper (and some reviews confirmed it worked OK!).
EDIT: Freedom's website is at
http://www.freedominput.com/
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